The PSNI says there's been an explosion at Shipquay Street in Derry, there are no reports of any injuries or damage.
Earlier, the area had been evacuated along with Ferryquay Street, Butcher Street and Bishop Street after an alert began in the Diamond area in the city centre.
In a statement issued a short time ago, Sinn Féin Councillor Gerry MacLochlainn condemned the incident.
He said those who planted this bomb need to tell the people of Derry how it will contribute to bringing about the new Ireland Republicans are striving for.
"The attack on a building society will not affect the global financial institutions nor the constitutional position of the North of Ireland but will seriously jeopardise jobs in the local economy. Not only are the jobs in the local branch now at risk but we will also have an effect on the tourism industry with people feeling Derry is unsafe to travel to.
"The city centre will now be closed for the rest of the day on what is the busiest shopping day of the week and the only people being disrupted by this attack are the citizens of this city.
"Thankfully this was a small device and no injuries and no serious damage was caused and the people who carried out the attack need to realise that they have been rejected by the Republican community and should desist immediately